By the end of the Labour Party Conference last week, it was clear that something had changed. For once, the media coverage was broadly positive. The same outlets that had played host to endless attempts to derail the party's leftward movement, and to undermine its elected leader, now granted a belated (and qualified) endorsement – if not of Jeremy Corbyn's project, exactly, then at least of its legitimacy and viability as a political force.

Sky News pronounced Corbyn 'king of all he surveys' in its assessment of his keynote speech. Lord Jim O'Neill – who got an ironic mention in the speech – has written in the Financial Times that Labour is 'poised to shake up the status quo'. The Daily Mail’s Quentin Letts delivered a backhanded compliment: 'Don’t scoff at Comrade Corbyn. His party’s got zip in its tank – and if the Tories don’t wake up, we’re all banjaxed.’ Even the Guardian, arguably Corbynism's most dedicated adversary, endorsed the leader’s speech as 'catching the zeitgeist'. Polly Toynbee, having spent the best part of the last three years trying to sink Corbyn, now says that he is 'winning the battle of ideas'.

So what changed? In a half-hearted attempt to save face, previously hostile commentators imply that Corbyn and his policies have somehow evolved to be at last worthy of endorsement by respectable opinion. Corbyn's oratory has really come along, they say. Yet his conference speech included the usual handful of fluffed lines, and the delivery towards the beginning sounded forced in places. If his usual critics had wanted to, they could have made a big deal of that – as they have done in the past. But concerns over Corbyn's oratorical skills or his self-presentation were always disingenuous. The occasional slip aside, Corbyn in 2015 was a pretty good speaker and communicator – far better than his predecessor, Ed Miliband. His proficiency is the legacy of more than thirty years as an activist and campaigner, not of a three-year crash course in the ways of the political establishment.

If it isn’t a change of style that's made the difference, it must be a change of substance. But Corbyn's new converts are hard pressed to say what that change is. The Guardian claims that Labour fought last year's election on 'policies from the past', while its new agenda is 'future-facing and concerned with dispersing the rights, wealth and power currently concentrated in a few hands’. But this egalitarian and democratic project has been at the heart of Corbynism, and the main source of its appeal, from the outset. Corbyn's Labour has deepened and extended its policy commitments since its popular but necessarily rushed 2017 election manifesto. But the new commitments emerging from the party conference – taxing second homes to create a 'solidarity fund' for supporting homeless people; giving workers a stake and a voice in the companies that employ them – are recognisably of a piece with previous ones. It isn’t Corbyn that has changed, but his opponents, as they now acknowledge that Corbynism has outlived their estimations of its life expectancy, and is the only plausible challenger to a Tory party in total disarray.

The biggest fear for those of us who welcome the direction in which Corbyn and his supporters are trying to move British politics has always been that they would either be crushed by their enemies (both within and outside the Labour Party) or sell out, capitulating to received wisdom about 'electability'. That has not happened. The party has emerged from its annual conference with its left-wing agenda intact and emboldened.

After a summer overshadowed by accusations of anti-Semitism, which the National Executive Committee tried to put an end to by adopting the full IHRA definition, supporters of Palestinian rights may have feared that the party's conciliatory stance would prevent it from speaking up for Palestine and holding Israel to account. The signs so far are that this has not happened either. Corbyn said Labour would ‘work with Jewish communities to eradicate anti-Semitism, both from our party and wider society’. He also reiterated his party's promise to recognise a Palestinian state immediately on taking office. Still more significant, though virtually unreported, was the passing of a motion to freeze arms sales to Israel.

The media focus has been on domestic economic policy, but it is arguably in foreign affairs that Corbyn’s challenge to political orthodoxy is most striking. He promised to put ‘diplomacy before tub-thumping threats’, and ‘no more reckless wars of intervention like Iraq or Libya'. He condemned the Tory collusion with the Saudi-led war on Yemen, which has displaced millions of people and killed tens of thousands of children, and said Labour would work ‘to resolve the world’s injustices, not standing idly by, or worse, fuelling them in the first place’ (an implied criticism of previous administrations). These are not new convictions on Corbyn’s part but lifelong commitments. Yet they are a radical departure from a cross-party historical norm in British politics.

Even on the Labour left, socially progressive domestic policies have often not been accompanied by an opposition to war and imperialism: Clement Attlee sent troops to Korea; Michael Foot, the Labour figure with whom Corbyn is most often (though misleadingly) compared, supported the Falklands War. Today’s political establishment has learned little from the disaster of Iraq – the consequences of which are still unfolding – and remains wedded to an imperial vision of Britain’s role in the world as a beacon of civilisation among backward and savage nations. Our leaders have continued to wreak havoc abroad, ostensibly for the good of the natives, acknowledging their mistakes only once it is too late to undo them – and then repeating them.

As with many of Corbyn's positions, his views on military intervention resonate more with people at large than they do with the political and media circles that pretend to represent ‘public opinion’. This resonance is double-edged. Corbyn’s anti-interventionism strikes a chord not only among those who share his outlook on global politics, but also among many whose war-weariness is bound up with an outlook that resents money being spent on ‘foreign aid’ and calls for a ‘tough’ line on immigrants and refugees.

But if there was a time when foreign and domestic policy could be treated as separate spheres, when Britain could do what it liked to the rest of the world without having to see or deal with the consequences, that time is long past. It isn’t a question of balancing obligations to a domestic population with quasi-charitable duties to distant others, but of drawing the connections between Britain’s actions in the world and the effects of those actions at home as well as abroad, whether in terms of terrorism, ecological and economic crisis, or the mass displacement of people. Our common interest lies in a total break with the patterns of the past. By refusing to change, Corbyn has already changed a lot.